Degradation of small simple and large complex lunar craters: Not a simple scale dependence

The crater record of a planetary surface unit is often analyzed by its cumulative size‐frequency distribution (CSFD). Measuring CSFDs involves traditional approaches, such as traditional crater counting (TCC) and buffered crater counting (BCC), as well as geometric corrections, such as nonsparseness correction (NSC) and buffered nonsparseness correction (BNSC). NSC and BNSC consider the effects of geometric crater obliteration on the CSFD. On the Moon, crater obliteration leads to two distinct states in which obtained CSFDs do not match the production CSFD—crater equilibrium and nonsparseness. Crater equilibrium occurs when each new impact erases a preexisting crater of the same size. It is clearly observed on lunar terrains dominated by small simple craters with steep‐sloped production CSFDs, such as Imbrian to Eratosthenian‐era mare units. Nonsparseness, on the other hand, is caused by the geometric overlap of preexisting craters by a new impact, which is also known as “cookie cutting.” Cookie cutting is most clearly observed on lunar terrains dominated by large craters with shallow‐sloped production CSFDs, such as the pre‐Nectarian lunar highlands. We use the Cratered Terrain Evolution Model (CTEM) to simulate the evolution of a pre‐Nectarian surface unit. The model was previously used to simulate the diffusion‐induced equilibrium for small craters of the lunar maria. We find that relative to their size, large craters contribute less to the diffusion of the surrounding landscape than small craters. Thus, a simple scale dependence cannot account for the per‐crater contribution to degradation by small simple and large complex craters

Gridmapping the northern plains of Mars: Geomorphological, Radar and Water-Equivalent Hydrogen results from Arcadia Plantia

A project of mapping ice-related landforms was undertaken to understand the role of sub-surface ice in the northern plains. This work is the first continuous regional mapping from CTX (“ConTeXt Camera”, 6 m/pixel; Malin et al., 2007) imagery in Arcadia Planitia along a strip 300 km across stretching from 30°N to 80°N centred on the 170° West line of longitude. The distribution and morphotypes of these landforms were used to understand the permafrost cryolithology. The mantled and textured signatures occur almost ubiquitously between 35° N and 78° N and have a positive spatial correlation with inferred ice stability based on thermal modelling, neutron spectroscopy and radar data. The degradational features into the LDM (Latitude Dependent Mantle) include pits, scallops and 100 m polygons and provide supporting evidence for sub-surface ice and volatile loss between 35-70° N in Arcadia with the mantle between 70-78° N appearing much more intact. Pitted terrain appears to be much more pervasive in Arcadia than in Acidalia and Utopia suggesting that the Arcadia study area had more wide-spread near-surface sub-surface ice, and thus was more susceptible to pitting, or that the ice was less well-buried by sediments. Correlations with ice stability models suggest that lack of pits north of 65-70° N could indicate a relatively young age (~1Ma), however this could also be explained through regional variations in degradation rates. The deposition of the LDM is consistent with an airfall hypothesis however there appears to be substantial evidence for fluvial processes in southern Arcadia with older, underlying processes being equally dominant with the LDM and degradation thereof in shaping the landscape

The high-resolution map of Oxia Planum, Mars; the landing site of the ExoMars Rosalind Franklin rover mission

This 1:30,000 scale geological map describes Oxia Planum, Mars, the landing site for the ExoMars Rosalind Franklin rover mission. The map represents our current understanding of bedrock units and their relationships prior to Rosalind Franklin’s exploration of this location. The map details 15 bedrock units organised into 6 groups and 7 textural and surficial units. The bedrock units were identified using visible and near-infrared remote sensing datasets. The objectives of this map are (i) to identify where the most astrobiologically relevant rocks are likely to be found, (ii) to show where hypotheses about their geological context (within Oxia Planum and in the wider geological history of Mars) can be tested, (iii) to inform both the long-term (hundreds of metres to ∼1 km) and the short-term (tens of metres) activity planning for rover exploration, and (iv) to allow the samples analysed by the rover to be interpreted within their regional geological context

The geography of Oxia Planum

We present the geography of Oxia Planum, the landing site for the ExoMars 2022 mission. This map provides the planetary science community with a framework to understand this, until recently, unexplored area. The map comprises (1) a mosaic of the panchromatic Context Camera (CTX) Digital Elevation Models (DEM) and Ortho Rectified Images (ORI) controlled to the High Resolution Stereo Camera (HRSC) multiorbit Digital Elevation Models (DEM) and (2) a mosaic of Colour and Stereo Surface Imaging System (CaSSIS) synthetic colour data products, registered to the CTX ORI mosaic. We define a grid of exploration quadrangles (quads) and an informal group of geographic regions to describe Oxia Planum. These regions bridge the scale gap between features observed on large areas (∼100s km2) and the local geography (10s km2) relevant to the Rosalind Franklin rover’s operations in Oxia Planum

The high-resolution map of Oxia Planum, Mars; the landing site of the ExoMars Rosalind Franklin rover mission

This 1:30,000 scale geological map describes Oxia Planum, Mars, the landing site for the ExoMars Rosalind Franklin rover mission. The map represents our current understanding of bedrock units and their relationships prior to Rosalind Franklin’s exploration of this location. The map details 15 bedrock units organised into 6 groups and 7 textural and surficial units. The bedrock units were identified using visible and near-infrared remote sensing datasets. The objectives of this map are (i) to identify where the most astrobiologically relevant rocks are likely to be found, (ii) to show where hypotheses about their geological context (within Oxia Planum and in the wider geological history of Mars) can be tested, (iii) to inform both the long-term (hundreds of metres to ∼1 km) and the short-term (tens of metres) activity planning for rover exploration, and (iv) to allow the samples analysed by the rover to be interpreted within their regional geological context

Die frühe Impaktgeschickte des inneren Sonnensystems und Verbindungen zu zukünftigen bemannten and robotischen Missionen zum Mond

The lunar and mercurian cratering records provide valuable information about the late accretion history of the inner Solar System. However, our understanding of the origin, rate, and timing of the impacting projectiles is far from complete. Different late accretion models including single and multiple impactor populations may explain the early lunar bombardment history. The single impactor population model explains the exponential decay of impactors over time (e.g., Neukum, 1983; Neukum & Ivanov, 1994; Hartmann, 1995), and the Late Heavy Bombardment (LHB) or lunar cataclysm model suggests different impactor populations with a rapidly increasing impact flux at 3.9 Gyr (Ryder, 1990, 2002). The primarily aim of this work is to test various accretion models and improve the lunar production function (PF) by re-evaluating its shape to infer potential impactor populations. To learn more about these projectiles, we can examine crater size-frequency distributions (CSFDs) on the Moon and Mercury. This PhD thesis re-investigates the crater populations of large (D ≥ 300 km) lunar and mercurian basins using the buffered crater counting (BCC) and buffered non-sparseness correction (BNSC) techniques. BSNC is a novel CSFD technique, which takes crater obliteration on highly cratered surfaces into account, thus providing more accurate measurements for the frequencies of smaller crater sizes. The BNSC-corrected CSFDs of individual basins, particularly at smaller crater diameters increase compared to the crater frequencies derived from the BCC technique alone. Furthermore, a new basin catalogue of 94 basins has been produced on Mercury, 80 of which have been classified as certain or probable, 1.7× times more than previously recognized. However, this number of basins has been estimated to represent roughly half of the expected basin record, where basins older than Borealis have been obscured by different processes (e.g., higher impact melt production, volcanism, subsequent impacts, and viscoelastic relaxation of basins). Consequently, if the Neukum (1983) and Neukum et al. (2001a) theories are correct that the impactor population in the inner Solar System did not change over time, one could expect that the summed CSFDs of basins in different time periods maintain a single shape following the lunar PF. Contrary to previous studies, the shape of summed CSFDs of Pre-Nectarian (excluding South Pole-Aitken Basin), Nectarian (including Nectaris) and Imbrian (including Imbrium) basins show no statistically significant differences, and thus provide no evidence for a change of impactor population bombarded the lunar surface. Similarly, the results on the shape of summed CSFDs of Pre-Tolstojan and Tolstojan basins on Mercury are consistent with the lunar study. The secondary aim is to find potential key landing sites for future human and robotic exploration missions with sample return capability on the lunar surface, which could target key sampling locations in order to verify the preferred late accretion model and refine the lunar chronology model, and thus, the absolute model ages (AMA) of different geologic units on the Moon and other terrestrial planets. In order to do so, this dissertation focus on the exploration of the South Pole-Aitken basin with the main focus on the south polar region of the Moon, a region that has not been visited by any human missions, yet exhibits a multitude of scientifically important locations – the investigation of which address long-standing questions in lunar research. The findings show that a human-assisted robotic mission to the South Pole-Aitken basin, can address all seven US National Research Council (2007) lunar science concepts, and would be a valuable resource to reveal the early history and evolution of the Solar System.Die Krater auf dem Mond und Merkur liefern wertvolle Informationen über die späte Akkretionsgeschichte des inneren Sonnensystems. Unser Verständnis von Ursprung, Geschwindigkeit und Zeit der impaktierten Projektile ist nicht jedoch vollständig. Verschiedene Modelle der späten Akkretion, einschließlich einzelner und mehrerer Impaktorpopulationen, können die frühe Impaktgeschichte des Mondes erklären. Das Einzelimpaktor-Populationsmodell erklärt die exponentielle Verringerung der Impaktoren im Laufe der Zeit (z. B. Neukum, 1983; Neukum & Ivanov, 1994; Hartmann, 1995), und das “Late Heavy Bombardment” (LHB) - oder “lunar cataclysm”-Szenario schlägt unterschiedliche Impaktorpopulationen vor, wobei eine signifikante Erhöhung der Impaktoreinschläge vor 3,9 Milliarden Jahren auftritt (Ryder, 1990, 2002). Das Hauptziel dieser Arbeit ist die verschiedenen Akkretionsmodelle zu testen und die Produktionsfunktion (PF) für den Mond zu verbessern, indem ihre Form neu bewertet wird, um auf potenzielle Impaktorpopulationen zu schlussfolgern. Um mehr über diese Projektile zu erfahren, können wir Kratergrößen-Häufigkeitsverteilungen (CSFDs) auf dem Mond und Merkur untersuchen. In dieser Doktorarbeit werden die Kraterpopulationen der großen (D ≥ 300 km) Mond- und Merkurbecken mithilfe der Techniken “Buffered Crater Counting” (BCC) und “Buffered Non-Sparseness Correction” (BNSC) erneut untersucht. BSNC ist eine neuartige CSFD-Technik, die die Auslöschung von Kratern auf stark verkraterten Oberflächen berücksichtigt und somit eine genauere Messung für das Auftreten kleinerer Krater ermöglicht. Die BNSC-korrigierten CSFDs einzelner Becken, insbesondere der mit kleineren Kraterdurchmessern, nehmen im Vergleich zu den Kratehäufigkeiten zu, die allein von der BCC-Technik abgeleitet wurden. Darüber hinaus wurde ein neuer Becken-Katalog mit 94 Becken auf Merkur erstellt, von denen 80 als sicher oder wahrscheinlich eingestuft wurden, 1,7-mal mehr als bisher bekannt. Diese Anzahl an Becken stellt schätzungsweise ungefähr die Hälfte aller erwarteten Becken dar. Becken, die älter als Borealis sind, wurden durch verschiedene Prozesse (z. B. hohe Schmelzproduktion, Vulkanismus, Viskoelastische Relaxation von Becken) überprägt. Wenn die Modelle von Neukum (1983) und Neukum et al. (2001a) richtig sind und sich die Impaktorpopulation im inneren Sonnensystem im Laufe der Zeit nicht verändert hat, könnte man erwarten, dass die aufsummierten CSFDs von Becken verschiedener Zeiträume Neukum’s PF folgen. Im Gegensatz zu früheren Studien zeigt die Form der summierten CSFDs der Becken von Pre-Nectarian (ohne South Pole-Aitken Becken), Nectarian (einschließlich Nectaris) und Imbrian (einschließlich Imbrium) keine statistisch signifikanten Unterschiede und liefert daher keine Hinweise auf eine Änderung der Impaktorpopulation, die die Mondoberfläche bombardierte. Die Ergebnisse der Pre-Tolstojan- und Tolstojan-Becken auf Mekur stimmen mit denen der Mondstudie überein. Das zweite Ziel dieser Arbeit besteht darin, potenzielle Landestellen für zukünftige bemannten und robotischen Missionen auf der Mondoberfläche zu finden, von denen Proben zur Erde zurück gebracht werden können. Die untersuchten Landestellen zielen darauf ab, Proben zu sammeln, um das bevorzugte Modell der späten Akkretion zu verifizieren und das Modell der Mondchronologie zu verfeinern. Dies wird schließlich das absolute Modellalter (AMA) verschiedener geologischer Einheiten auf dem Mond und anderer terrestrischer Planeten verbessern. Diese Dissertation fokussiert sich deshalb auf die Erforschung des South Pole-Aitken Beckens und legt einen Schwerpunkt auf die Südpole des Mondes, einer Region, die bisher von keiner bemannten Mission besucht wurde, jedoch eine Vielzahl von wissenschaftlich relevanten Orten aufweist. Das Untersuchen dieser Orte wird langjährige Fragen der Mondforschung beantworten können. Die Ergebnisse zeigen, dass alle sieben Mondforschungskonzepte des US National Research Council (2007) mit einer von Menschen unterstützten Robotermissionen zum South Pole-Aitken Becken untersucht werden können. Dies ist von großer Wichtigkeit, um die frühere Impaktgeschichte des Mondes und die Entstehung des Sonnensystems besser zu verstehen

Proposed elements and an approach to evaluate the astrobiology potential of landing sites on Mars

The targeting of Mars surface missions aiming at astrobiology relevant analyses, requires a specific and also a complex evaluation of landing sites, besides the evaluation of engineering constraints. This chapter presents the evaluation of some aspects of the two remaining landing site candidates (Oxia Planum and Mawrth Vallis) for the ESA ExoMars 2020 rover, as examples to highlight the geological and astrobiological aspects in general. Past robotic missions to Mars mainly provided insight into the local geological context by analyzing outcrops on the surface or drilling down to a few cm-s below that. These lessons learned should be used in the future to increase the scientific outcome. Next missions will increase the research capacity, thus the need for improved targeted sampling will be necessary for their sophisticated instruments. Furthermore, new aspects might be involved in landing site selection including those that support to better understanding the geological context. The evaluation of the preservation potential of biosignatures at the landing site candidates will be also high priority in mission planning, using various instruments from orbiters, such as infrared, hyperspectral and optical datasets of different resolutions. Preservation potential could be very roughly estimated from thermal inertia, which is usually elevated for the less weathered rocks. However, it is difficult to take into account these astrobiology relevant parameters as deep craters or steep slopes provided outcrops are dangerous locations for robotic missions. This chapter evaluates these aspects using the parameters of the ExoMars 2020 rover, which mission will be able to study the “deeper” subsurface and its astrobiological potential in details by drilling, as well as geophysical and geochemical instruments

Mawrth Vallis, Mars: A Fascinating Place for Future In Situ Exploration

International audienc